The Impact of Disk Fragmentation on Servers - Products

The Impact of
Disk Fragmentation
on Servers
By David Chernicoff
➔ Contents
Testing Server Disk Defragmentation........2
The Testing Environment...........................3
The Tests...................................................4
File Copy..................................................4
Backup.5
Anti-Virus Scan.........................................5
VHD Start.................................................6
VHD Save................................................6
Exchange Test One...................................6
Exchange Test Two....................................7
SQL Server Bulk Insert..............................7
Table Key Creation (measured in seconds).8
SQL Query 1 (Simple)...............................8
Conclusion...............................................8
The Impact of
Disk Fragmentation
on Servers
by David Chernicoff
Testing Server Disk Defragmentation
IT professionals responsible for server hardware well
understand the value that professional grade disk
defragmentation software brings to their servers. Storage
servers can experience high levels of disk thrashing (the
constant writing and rewriting of small amounts of data)
caused from excessive file fragmentation.
Problems in delivering services to users however are
difficult to directly trace to server fragmentation issues.
Network and application issues have a much more visible
impact on the performance of network-based services,
especially when problems with those functions are
encountered. But with the negative impact on ROI that
network performance problems cause, IT pros would be
ill-advised to overlook the advantages that assuring the
optimization of the underlying hardware infrastructure can
bring. Optimal disk performance translates into better ROI.
Testing will bear this out.
We tested the impact of server disk defragmentation
by looking at common tasks that network servers, both
physical and virtual, encounter, ranging from maintenance
tasks such as server backup and anti-virus scans, to basic
knowledge worker tasks involving opening files stored on
the host server and virtual machines, and manipulating
email. We also looked at tasks that are more taxing on the
server, such as database queries, index creation, and bulk
updates. Each test was performed as the sole task on the
server.
When considering the results of our testing keep in mind
that a production environment will see significantly
heavier server use, which results in much greater potential
for ongoing disk fragmentation. In your production
environment with dozens, if not hundreds, of users
touching your server storage simultaneously, your disk
fragmentation can become severe in a very short time.
Preventing this fragmentation from affecting server
performance is an ongoing process.
2 The Impact of Disk Fragmentation on Servers
The Testing Environment
For our benchmark tests we used an HP ProLiant
DL380 G5 equipped with dual quad-core 2.83
GHzXeon processors, each with a 2x6MB L2 cache,
16 GB of RAM and seven 72 GB 10,000 RPM SCSI
drives attached to an HP Smart Array P400 controller
that has a 256 MB cache and that supports both
serial-attached SCSI and SATA drives. The volumes
we tested against were 30 GB, 80 GB, and 175 GB.
We used a 500 GB 7200 RPM locally attached SATA
drive for backup only. The server operating system
was Microsoft Windows Server 2008 Enterprise; the
application server software installed in VHDs was
Microsoft SQL Server 2008 and Microsoft Exchange
Server 2007. All server software was updated with
service packs, patches and hotfixes current as of
February 2009. The disk defragmentation software
used was Diskeeper Server.
The seven SCSI drives attached
to the array controller were
configured as two physical
drives. We used the first
physical drive, comprised
of two drives configured
as a RAID 0 stripe set for
maximum performance, for
the installation of the operating
system and all related fi les.
We configured the remaining
five drives as a RAID 5 stripe
set to be representative of the
We tested three levels of fragmentation, described
herein as low, medium, and high. We used the
Diskeeper Diskcrusher fragmentation utility to
create fragmented files and directories. We ran
all tests a minimum of three times with the results
reported here being the average of all test runs.
As shown in Table 1 the level of fragmentation and
Number of files
Avg. number of fragments per file
Number of fragmented files
Number of excess fragments
Percent Fragmented - Volume
Percent Fragmented - Data
Low
101,652
3.21
99,074
225,216
40%
51%
Medium
1,220,660
1.69
613,221
840,076
50%
58%
Free Space
22%
15%
Table 1: Fragmented disk test configurations
Figure 1: Fragmentation map of a havily fragmented disk
type of hardware storage configuration found in
most business environments. We performed all
applications, VHDs, and tests on the RAID 5 stripe
set. The volume size was dependent upon the test
level. As an example of the effect fragmentation
can have, the screen capture in Figure 1 shows
the Diskeeper fragmentation analysis of a severely
fragmented disk. The severe fragmentation
documented here will have a negative impact on
storage performance.
High
2,087,158
2.30
1,994,117
3,005,400
84%
91%
15%
Figure 2: Fragmentation map after automated
defragmentation by Diskeeper
The Impact of Disk Fragmentation on Servers 3
the number of affected
Low
Medium
High
files increases with each
Number of files
101,652 1,220,660 2,087,158
testing tier. The level
Percent Fragmented - Volume
0
0
0
of fragmentation you’ll
Percent
Fragmented
Data
0
0
0
encounter in production
Avg. number of fragments per file 0
0
0
environments is dependent
Number
of
fragmented
files
0
1
1
upon the level of use
Number
of
excess
fragments
0
2
4
and types of applications
the server deals with.
In all likelihood, if
Free Space
22%
15%
15%
your server storage
Table 2: Fragmentation map after automated defragmentation by Diskeeper
levels are consistently
exceeding 75 percent or
stopwatch. This is one of the most basic tasks done
so, you’ve begun aging data off of the servers or
with server data and, in a severely fragmented
you’re planning to add additional storage. While
environment, showed some of the most significant
fragmentation isn’t a direct result of reduced
performance improvements.
capacity, the chances for fragmentation increase
as free storage space decreases and the operating
system is forced to write data into an everFile Copy Tests
increasing number of non-contiguous spaces.
(measured in seconds)
By using an automated defragmentation process,
the same disk volume sees absolutely minimal
fragmentation even though it is in continual use by
applications and users (Figure 2).
We ran each set of tests for three iterations, and
then defragmented the storage using Diskeeper
to reduce or eliminate the disk fragmentation.
We repeated each test (also for three iterations)
and averaged the results. In the following test
descriptions and analysis, the comparisons are all
before and after defragmentation at each specific
fragmentation level tier. We did not do cross-tier
comparisons. All test times are reported in seconds.
The Tests
In our first set of tests we look at common
server tasks that are likely to be affected by
disk fragmentation. These tasks are all primarily
storage related; that is, the performance of the
storage media will have a primary impact on the
performance of these tasks.
File Copy
In the file copy test, a folder containing 5 GB
worth of files and sub-directories was copied from
the test volume to the boot volume of the server.
To minimize variables, the copy was done locally,
not across the network. We timed the test using a
4 The Impact of Disk Fragmentation on Servers
Fragmented
Defragmented
Low
44
39
Medium
72
60
High
97
54
The basic task of moving data from one location
to another on the server shows that a fragmented
disk has a major negative impact on the fi le copy.
Even the lightly fragmented low-level test showed
an improvement in copy time of over 11 percent,
while the copy that was done from the very highly
fragmented drive improved in time by almost 45
percent. Given how common the file copying task
is the benefit is clear. Defragmented disks are a
significant time saver for common user tasks.
While the limiting factor in doing a file copy from
the server to the client might be the available
network bandwidth, as technologies such as
Gigabit Ethernet become more common, the
base limiting factor will be how fast the operating
system can feed data to the network request,
which is directly impacted by fragmentation of the
data on the local drive.
Document Open
In this test, a 100-page Microsoft Word document
was opened from the server to a Windows XP
client running Microsoft Office 2007. The size of
the document was 3.3 MB.
Low
Medium
High
File Copy Tests
(measured in seconds)
Fragmented
Defragmented
44
72
97
39
60
54
Our test results showed performance
improvements of upwards of 30 percent. In the
case of any file load from server to client the
performance improvement will be determined by
just how badly fragmented is the file located on
the server. In our tests, the file was clearly badly
fragmented, significantly so at the highest level
of fragmentation testing. To prevent this type of
file fragmentation, the best methodology is an
ongoing background file defragmentation process,
the benefits of which are clearly demonstrated
by this test. And given how often this type of task
is performed in most business environments,
the value of the defragmentation cannot be
understated. As shown in this and the File Copy
test, basic data manipulation is much faster on
defragmented storage.
While different backup tools will be differently
affected by disk fragmentation, our tests showed
one simple fact; defragmented disks back up
faster. Individual runs demonstrated performance
improvements of up to 20 percent with our test
data set and the built-in Windows Server backup.
Our least effective test result, a large data backup
that can represent a significant amount of time,
still showed an improvement of 5 percent. Our
highest report results, which averaged a 17 percent
reduction in backup time, shows that reducing
or eliminating disk fragmentation prior to backup
will allow larger amounts of data to be backed
up, especially if time is a constraint in your
backup process. If backup is run as a background
application, reduced fragmentation will allow for
lower resource consumption necessary for the
backup process, minimizing further the impact of
the backup on active users of the storage.
Anti-Virus Scan
For the AV scan test we performed a complete
scan of the test volume using the Kapersky Lab
AntiVirus Version 6 Windows Server software,
current as of February 2009. The default
configuration of the AV software was used with
only the test volume selected for scanning. Timing
was done using the AV application.
Backup
In the first test, we backed up the test volume using
disk-to-disk backup as supported by Windows
Server Backup, which is a component of Windows
Server 2008. Backup was done using the VSS copy
method, which is designed to work with other
backup tools that would require that the archive and
backup information in the files remain unmodified.
We backed up to a SATA-attached dedicated hard
drive that was reformatted between tests. Timing was
done using the backup application.
Low
Medium
High
Backup Tests
(measured in seconds)
Fragmented
Defragmented
1193
1130
2787
2300
6960
6620
Low
Medium
High
Anti-Virus Scan Tests
(measured in seconds)
Fragmented
Defragmented
256
238
1485
1359
4428
4004
Many factors will have an impact on the speed
of a complete anti-virus scan of your storage.
The way the scanner works, the total number of
files that need to be scanned, the size of the files,
and the fragmentation level of the disk all have a
direct impact on the length of the AV scan process.
In our tests with the Kapersky Lab AV solution,
the disk defragmentation resulted in upwards of a
10 percent performance improvement—with the
improvement being more significant as the test
drives increased in size, number of test files, and
fragmentation.
The Impact of Disk Fragmentation on Servers 5
VHD Start
This test measured the amount of time it took to
launch the saved test virtual machine. The VM was
launched from a saved state and timing stopped
when the Hypervisor manager reported that the
VM was successfully started.
VHD Start Tests
(measured in seconds)
Fragmented
Defragmented
Low
62.3
51
Medium
60.7
58
High
55.3
47
With as much as a 17 percent improvement in
the start time of the test virtual machine, the
effects of fragmentation on the VHD are clear. This
fragmentation will also impact the performance
of the VM itself, because all of the additional I/O
necessary to read from a severely fragmented
VHD will reduce the performance of the virtual
computing environment. Fragmentation must
also be watched if your VMs are configured
with the dynamic disk option, which allows the
virtual machine to grow the size of its storage as
necessary. This means that as the size of the VHD
grows it will continue to fragment into the available
space on the hard drive. Making sure that the host
machine hard disk is regularly defragmented and
managed will improve the performance of virtual
machines running on the host and allow for the use
of dynamic disk allocation within the VM without
danger of disk performance issues.
Figure 3: Fragmentation map of VHD volume
Low
Medium
High
VHD Save Tests
(measured in seconds)
Fragmented
Defragmented
365.3
271.7
409.3
402
447.7
390.3
defragmentation, the VHD Save tests show quite
clearly the effect of writing a very large file to a
Even with significant free space of the disk, as
shown by the white space in the fragmentation
map (Figure 3), major fragmentation can still occur
even without VHD test volume.
VHD Save
This test measured the length of time required to
save the test virtual machine. From the Hypervisor
manager, the running machine was saved and
timing stopped when the manager reported the
save complete.
With test results indicating as much as a
25 percent performance improvement after
6 The Impact of Disk Fragmentation on Servers
Figure 4: Fragmentation map after automated
defragmentation by Diskeeper.
fragmented hard drive. The more fragments on
the drive the less likely it will be that a large file
can be written contiguously. And in the world
of virtualization, large files are the standard,
and the need to be able to read and write
those files with a minimum of fragmentation
is a requirement to meet the basic ROI needs
of the enterprise. Automated background
defragmentation results in a major reduction in
fragmentation even with an active VHD (Figure
4). Regular use of the background defragmenter
will continue to minimize fragmentation.
Server Application Tests
In the server application tests we looked at the
impact of fragmented storage on server-based
applications. Other factors will have an impact
on the overall performance of these applications;
optimizing storage strategies, including
defragmentation, reduces the impact of storage
performance on the overall application performance.
Exchange Test One
In this first Exchange test, the client, a Windows XP
Professional Workstation running Office 2007, uses
Outlook to open 100 messages from the server. One
hundred messages are highlighted then opened
simultaneously. Timing starts when the open is
launched and stops when all of the messages have
Exchange Test One
(measured in seconds)
Fragmented
Low
Defragmented
7.7
7
Medium
10.7
8.6
High
18.4
11.6
been opened and console control returns.
While the impact of server fragmentation gets
significantly greater as the disk becomes more
fragmented, even the common lower levels of
fragmentation will have a large impact on user
response time when you consider that hundreds
of users may be accessing the data store at the
same time. Delayed response time for email
users is a generator of a large percentage of help
desk calls, and implementing a defragmentation
strategy can help to solve the problem. As our
tests show, allowing the data to become seriously
fragmented can have a major negative impact on
the Exchange user experience with a 40 percent
reduction in performance in our highly fragmented
test environment. Good defragmentation strategies
result in fewer help desk calls.
Exchange Test Two
In this test, the contents of an existing folder were
Exchange Test Two
(measured in seconds)
Fragmented
Low
Defragmented
9
8
Medium
13.8
9
High
24.9
12.3
moved to a new folder. Time to complete was
measured from the client side.
A new folder was created and the contents
of the Inbox were moved to the new folder.
With our heavily fragmented test environment
showing a greater than 50 percent performance
improvement after defragmentation it’s clear that
this test was extremely sensitive to higher levels
of fragmentation on the server. If users are often
found reorganizing the data in the Exchange
mailbox, the impact of fragmentation can be quite
severe.
SQL Server Bulk Insert
We tested SQL Server 2008 with a bulk insert of
50,000 rows of data. The bulk insert is often the
SQL Server Bulk Insert Tests
(measured in seconds)
Fragmented
Low
Medium
High
Defragmented
22.1
20.9
31
25
53.3
33.4
fastest method of getting data into a SQL Server
database.
As has been seen with the Exchange tests, a highly
fragmented database structure can have a severe
negative impact on loading and extracting data
from server applications, with our test showing
a performance improvement of 40 percent
in the most heavily fragmented environment.
Because Microsoft offers APIs for moving open
The Impact of Disk Fragmentation on Servers 7
files, defragmentation software is able to safely
work on database files without risk of data loss
or corruption. Loading data into a defragmented
environment not only improves load times but
reduces the amount of disk thrashing necessary to
manipulate the data and the amount of work that
is necessary to later defragment the database.
Table Key Creation (measured in
seconds)
In this test each table was opened, a field was
selected as the primary key, and the change was
saved.
The table key creation times are directly
related to how much data SQL Server had
to touch, and the level of fragmentation that
had to be dealt with. SQL Server 2008 does a
very good job of managing its databases, but
defragmentation shows appreciable improvement
in the performance of tasks such as this with a
performance improvement of over 11 percent in
the most fragmented environments.
With the SQL queries, the two tests differ primarily in
the amount of data that SQL Server returns in response
to the query. The tests depict the effects of manipulating
the data on a fragmented drive with peak performance
improvements of approximately 18 percent.
Measured
in seconds
Table 1
Fragmented
Table 2
Defrag­ Frag­
mented mented
Low
Medium
High
12.5
12.4
25.5
12
14.1
20.6
15.9
18.23
32.4
Fragmented
35.3
33.3
Medium
41.5
38.5
High
61.3
50.8
Conclusion
The single, consistent result that appears in all
of our tests is that defragmented server drives
using Diskeeper deliver better performance. Every
application that touches the hard drive will benefit
from a good tool that defragments and manages
the files on your servers.
Almost every role filled by Windows servers in your
computing environment will benefit from the use
of disk defragmentation software. The simplest file
and print services delivery requires a significant
amount of disk I/O and will easily benefit from
file defragmentation. As our simple tests show,
even Exchange and SQL Servers benefit from
defragmentation; reading and writing data with either
application simply works better when the files are
not fragmented. The result is improved performance.
26
32.3
51
Low
23.9
22.3
Medium
28.2
24.8
High
43.5
33
Defragmented
Low
14.9
17.1
25.3
Defragmented
8 The Impact of Disk Fragmentation on Servers
Defrag­
mented
SQL Query 1 Test
(measured in seconds)
Fragmented
SQL Query 2 Test
(measured in seconds)
Table 3
Frag­
mented
SQL Query 1 (Simple)
SQL Query 2 (Complex)
Defrag­
mented
Table 4
Frag­
mented
Defrag­mented
24.2
30.4
46.7
35.4
49.1
68.8
33
43.8
61.3
Throwing more storage resources (hardware) at a
problem should be the last resort, because it only
masks the potential problems that intelligent disk
defragmentation addresses. Quicker response
time in databases and mail servers means that
more time is spent getting work done, rather than
waiting for information to be delivered.
Diskeeper is the only true server
defragmentation software that runs silently
in the background, continually improving
performance. With the current economic and
business environment, maximizing ROI becomes
even more critical. Adding Diskeeper to your
server toolkit gives you the ability to get the
maximum speed from your storage subsystems
of your existing hardware.
David Chernicoff is a technology consultant with
a focus on the mid-market space, Windows IT Pro
Senior Contributing Editor, founding Technical
Director for PC Week Labs (now eWeek), former
Lab Director for Windows NT Magazine/Windows
2000 Magazine (now Windows IT Pro) and
formerly Chief Technology Officer for a network
management tools ISV. David has been writing
computer-related feature and product reviews for
more than 20 years and is coauthor of a number of
operating system books, ranging from the Windows
NT Workstation: Professional Reference (New
Riders Publishing), to the Microsoft Windows XP
Power Toolkit (Microsoft Press), as well as over
a dozen eBooks on topics ranging from network
switching topologies to production FAX technology.
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The Impact of Disk Fragmentation on Servers 9